Fish

Did you know that sharks are actually a species of fish? Fish can be found in nearly all aquatic environments, from high mountain streams to the deepest depths of the oceans. Fish have specialized gills that allow them to breathe under water and nearly all fish that swim during the daylight hours, have color vision that is at least as good as a human's. With over 32,000 species, fish exhibit greater species diversity than any other group of vertebrates (having backbones).